Your Name _______________________Period ______ Date __________
Chapter 9 Earth Science Word Study – A View of Earth's Past
Directions: Study the following words by reading and rereading them each
evening so you will be prepared for the word study test each week. You may
use one index card to write as many words and definitions on as possible to use
for the test. The card must written in ink, be in your handwriting, and have
your name, period, and chapter recorded in the top, right corner with no
obvious erasures or mark outs. If all the criteria are met, you may use your
index card during the test. It will then be stapled to your test.
1.) geologic column - an ordered arrangement of rock layers that is based
on the relative ages of the rocks and in which the oldest rocks
are at the bottom
2.) era - a unit of geologic time that includes two or more periods
3.) period - a unit of geologic time that is longer than an epoch but
shorter than an era
4.) epoch - a subdivision of geologic time that is longer than an age but
shorter than a period
5.) ma - stands for "mega-annum" which means "one million years"
6.) eon - the largest unit of geologic time/there are four eons; the
Hadean eon, the Archean eon, the Proterozoic eon, and the
Phanerozoic eon/the
7.) Precambrian time - the first three eons of Earth's history and the
longest span of time which lasted 4 billion years/it started with
the formation of Earth to the beginning of the Paleozoic era from
4.6 billion to 542 million years ago/there are very few fossils so
dividing the Precambrian Time is difficult/life on the Earth
consisted of very basic forms like bacteria and other
single-celled organisms
8.) Phanerozoic eon - the last and most recent eon which contains the
majority of the fossils found so far on Earth and which is the
shortest eon in time
9.) evolution – a heritable change in the characteristics within a
population from one generation to the next; the development of
new types of organisms from preexisting types of organisms
over time
10.) Paleozoic Era – the geologic era that followed the Precambrian time
and that lasted from 542 million to 251 million years ago/there
are abundant numbers of fossils found from this time
period/because there are so many fossils scientists have divided
this era into seven periods/life began to diversify and flourish,
producing multi-cellular organisms that included fish,
amphibians and reptiles
11.) mass extinction – an episode in geologic time in which large numbers
of species become extinct/many scientists believe there have
been at least five of these types of events
12.) Mesozoic Era – the geologic era that lasted from 251 million to 65.5
million years ago; this era is also called the “Age of
Reptiles”/there are three periods in this era/Birds and mammals
first appeared during this era as well.
13.) Cenozoic Era – the current geologic era, which began 65.5 million
years ago; also called the “Age of Mammals”/there are three
periods in this era/This era is identified by the widespread
development of mammals, including the human species.